Brush holder



Aug. 14, 1945. 1... D. LEACH ETAL BRUSH HOLDER Filed May 1, 1944 [ripen/507's mm (M Patented Aug. 14, 1945 BRUSH HOLDER Lawrence D. Leach and Leonard G. Strom, Minneapolis, Minn. Leach said Strom assignor to said Application May 1, 1944, Serial No. 533,474

3 Claims.

Our invention relates to removable brush hol ders for electric motors and has for its object the provision of a simple, strong, and quick-cooling holder of this type.

We are aware that prior to our invention there were numerous brush holders adapted tobe inserted into openings in the commutator end of electric motor frames, and we are likewise aware that brush holders of the same general shape and design as the brush holder illustrated in the attached sheet of drawings are old in the art. The object of our invention is to provide a novel frame for such brush holders which, in combination with the Bakelite or other plastic material, will provide a greatly reinforced brush holder at a minimum of cost.

Furthermore, we have found in those brush holders made entirely of plastic material or in those holders having disconnected metal inserts embedded in the plastic material, the heat that is generated by frictional engagement of the brush and commutator is not carried. away from the base end of the holder; and, as a result of this concentration of heat, the plastic base becomes so hot that it decomposes and chips oil. This breaking down, due to undissipated heat, results in the necessity of replacing many brush holders long before the upper part has begun to show the effects of heat and wear.

We have found that by constructing a brush holder with a frame of our novel type and design,

that the heat which normally concentrates at the base of the holder is rapidly distributed throughout the other portions of the holder including the body and head portions. As a result of this dissipation of heat the temperature throughout the entire holder is raised considerably but not raised high enough to have a damaging or destructive effect upon the plastic material. At the same time the temperature at the base is lowered below the point of destruotib-ility.

With the above and other objects in view. which will appear as the description proceeds, the invention resides in the combination and arrangement of parts and in the details of construction hereinafter described and claimed. Changes in the precise embodiment of the invention shown can obviously be made without departing from. the scope of the invention.

In the accompanying drawing, in which like characters indicate like parts throughout the several views:

Fig. 1 is a top elevation;

Fig. 2 'is a side elevation;

Fig. 3 is a vertical axial sectional view taken on the line 33 of Fig. 1;

Fig. 4 is a transverse sectional View taken on the line 44 of Fig. 2; and

Fig. 5 is a perspective view of the novel frame structure before being embedded into the Bakelite or other plastic material, having proper insulating qualities.

Referring more particularly to the drawing, the holder is molded with a flattened body portion 6 having rounded ends I and 8. Integrally cast with the plastic body 6 is a collar-like head 9, round in cross section, as shown in Fig. 1.

The base portion I ll of the body is of less width than the diameter of head 9 as shown in Fig. 2. However, at H the flattened body portion extends out slightl beyond the peripheral edge of head 9 forming a centrally located shoulder i2 and a fiat edge surface I3. I

Embedded within the plastic material of the holder is our novel frame which is made up of a notched centrally located supporting leg I 4, elongated head, and base plates l5 and I6 respectively, and a depending terminal arm ll.

Base plate'lfi is provided with a pair of opposed upstanding anchor plates l8 and with a pair of laterally spaced rectangular openings 19. It may be seen by reference to Fig. 5, that the maximum width of supporting leg l4 coincides substantially with the space between the two upstanding sulpporting anchor plates l8 and the base of leg I4 is soldered or otherwise secured to base plate I6 and anchor plates I8. The upper portion of supporting leg I4 is soldered or 1 otherwise secured to the central portion of head plate l5. Head plate I5 is provided with a pair of laterally spaced round holes 20, the diameter of which openings is slightly greater than the length of the rectangular openings 19 in the base plate l6. Depending terminal arm I! is provided with enlarged terminal boss 2i through which there extends an opening 22.

Further openings 23 are in the terminal arm. The function of these are the same as the notches in the leg l4, that is to provide more surface for the Bakelite or plastic to adhere to, thus imparting greater rigidity to the structure.

It will be observed by reference to Figs. 3 and 5 that the openings 20 in the head plate I5 and the opening 22 in the terminal boss 2| are screw threaded. These holes may be tapped or threaded before the plastic material is molded around the frame, however, it has been found to be best to thread these holes after the application of the plastic to frame member.

As shown in Figs. 3 and 4 the plastic ma terial is so molded as to provide parallel guide passage 23 inter-communicating between the rectangular openings IQ of the base plate l6, and the round openings of the head plate IS. A pair of rectangular carbon members 24, having substantially the same cross sectionas the holes IS in the base plate l6, project downward from the base through the openings l9. Embedded in the upper portions of the carbon members 24 are flexible small wire or cable members 25 which extend out the upper ends and connect to contact plates 26. A pair of coil springs 21 are interposed between the contact plaies 26 and the carbon members 24 and the upper portions of carbon members being reduced to provide a shoulder for the coil springs 21.

Screw 28 is shown as being threaded into terminal boss 2|.

Plastic covered metallic closures 29 are shown as having screw threaded engagement with apertures 20 in the head plate l5. Plastic head 9 is provided with diametrically opposed openings 30 thru which may be extended, screws or threaded bolts, for the purpose of securing the holder in position in the motor frame.

Coil springs 21 are of a length greater than the axial length of the parallel guide passages 23 and therefore they exert a constant, but gentle downward or outward pressure against the carbon members 2| thus keeping carbon members 24 in contact with the commutator of the electric motors in which they are placed, until said carbon members have been reduced in length by such wear to a point where they mustbe replaced.

This replacement is accomplished merely by the unscrewing of closure members 29 withdrawing the assembled contactplate, coil spring and carbon member and replacing same.

The electricity picked up by the brush or carbon member 24 runs up theelectric wire or cable member 25 to contact plate 26, thence to metallic closure 29, to head plate I5 down terminal arm 23 to terminal boss 2| and out to point of storage or consumption through electric wire or the like attached to screw 28.

The electrical circuit, above described, is the only circuit possible in brush holders not having a connected metal frame. However, with our device there are several alternative and supplementing circuits for the electricity picked up by the carbon brush members. For instance, all the electricity picked up by the brush must necessarily be discharged through the base member 16 and up through the central supporting leg [4 to head plate l5 and thence down through the terminal arm IT. This is true because carbon members 24, when in contact with the commutator, are always in tight frictional engagement with rectangular openings I 9 through which they pass.

While it is understood that our novel frame member can be made of any metal which is a good conductor of electricity and heat, we have found in practice that brass is very satisfactory for this purpose.

What-we claim is:

'1. In a monolithic brush holder molded from insulating material and comprising a flattened body portion and an enlarged heada metallic frame member consisting of a supporting leg, a base plate, a head plate, and a terminal arm, said base plate having laterally spaced rectangular openings, said head plate having laterally spaced circular openings aligned with the openings in the base plate, said supporting leg being secured at the base and head plates intermediate the spaced openings, said molded body portion having laterally spaced parallel guide passages, intercommunicating between the aligned openings in the head and base plates, and said terminal arm being secured to and depending from the head plate and terminating in a screw threaded boss. the outer surface of said boss being flush with the side surface of the molded body portion.

2. In a monolithic brush holder molded from insulating material and comprising a flattened body portion and an enlarged head-a metallic frame member consisting of a supporting leg, a base plate, a head plate, and a terminal arm, said base plate having'laterally spaced rectangular openings, said head plate having laterally spaced circular openings aligned with the openings in the base plate, said supporting leg being secured at the base and head plates intermediate the spaced openings, said molded body portion having laterally spaced parallel guide passages, intercommunicating between the aligned openings in the head and base plates, said base plate being provided with a pair of centrally located laterally spaced upstanding anchor flanges embracing the base end of the supporting leg, the lower surface of said base plate constituting the base end surface of said holder, and the outer faces of said anchor flanges being exposed on the flat sides of the body portion.

3. In a monolithic brush holder molded from insulating material and comprising a flattened body portion and an enlarged head-a metallic frame member consisting of a supporting leg, a base plate, a head plate, and a terminal arm, said base plate having laterally spaced rectangular openings, said head plate having laterally Spaced circular openings aligned with the openings in the base plate, said supporting leg being secured at the base and head plates intermediate the spaced openings, said molded body portion having laterally spaced parallel guide passages, intercommunicating between the aligned openings in the head and base plates, said supporting leg being notched on its edges, and said terminal arm being provided with a plurality of plastic receiving apertures.

LAWRENCE D. LEACH. LEONARD G. STROM. 

